Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981a%26a....96..278w&link_type=abstract
Astronomy and Astrophysics, vol. 96, no. 1-2, Mar. 1981, p. 278-282. NSF-supported research.
Astronomy and Astrophysics
Astrophysics
19
Electron Transitions, Helium, Planetary Nebulae, Radiative Recombination, Radio Spectra, Abundance, Electron Density (Concentration), H Alpha Line, H Beta Line, Hydrogen Recombinations, Spectral Line Width
Scientific paper
The H 76 alpha transition has been observed using the Effelsberg 100-m telescope and the H 140 alpha transition has been observed using the Arecibo telescope towards a selection of planetary nebulae. The Arecibo results were negative suggesting that collisional broadening (of the line) plays an important role at frequencies below 5 GHz in many planetary nebulae. On the basis of the Effelsberg observations, it is concluded that there is presently reasonable agreement between optical and radio determinations of the electron temperatures. The electron density and helium abundance derived from radio observations of NGC 7027 seem consistent with the optical values. The helium abundance in NGC 7027 is derived to be 0.14 by number relative to hydrogen.
Churchwell Edward
Terzian Ye.
Walmsley Charles Malcolm
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